A new report says 30,000 people in South Sudan's Unity State are on the brink of starvation and death amid growing hunger in the war-ravaged country.

The report from U.N.-backed food security experts warns four Unity State counties could slide into famine conditions by the end of the year without immediate humanitarian assistance.

Nearly four million South Sudanese in all, about a third of the population, are said to be in a food crisis or emergency, mostly in Unity, Jonglei and Upper Nile States.

A joint statement from three U.N. relief agencies (UNICEF, the FAO, and the World Food Program) called for South Sudan's warring parties to allow unrestricted access to the affected areas.

South Sudan's government has been battling rebels led by former vice president Riek Machar since December of 2013. The fighting has displaced an estimated 2.6 million people.

The new report was produced by analysts with the Integrated Food Security Phase Classification program.

The researchers said while hunger may decrease somewhat during harvest season, the number of food-insecure households is almost 80 percent higher than at this time last year. It said families are struggling to cope with the violence, erratic rainfall, depleted livelihood options, and high prices for food and fuel.

The government and rebels signed a peace deal at the end of August but each side has accused the other of repeated violations.